Archive | Fish

PALO ALTO, Calif., Oct. 7 (UPI) — The number of connections, or synapses, in a particular region of the brain varies between night and day and appears to be regulated by a gene, researchers say.

Stanford University scientists have been studying what happens in the brain while you sleep and how the circadian clock and sleep affect neuron-to-neuron connections, a university release says.

Why we need to sleep and how, exactly, sleep is restorative are unanswered questions in biology.

Using zebrafish, a popular aquarium fish that, like humans, are active during the day and sleep at night, they studied “synaptic plasticity,” the ability of synapses to change strength and even form and erase.

“This is the first time differences in the number of synapses between day and night and between wake and sleep have been shown in a living animal,” researcher Lior Appelbaum, said.

They theorize that nighttime changes in the number and strength of synapses — the synaptic plasticity — help recharge the brain and, in turn, benefits memory, learning and other functions.

“It gets ready for new activity by telling the neurons they have to shut down synapses during this time of day but increase them at other times of the day,” he said.

They also identified a gene that appears to be involved in regulating the rhythmic changes in synapses.

RALEIGH, N.C., Oct. 6 (UPI) — In a surprise finding, U.S. researchers say fish located near coal-fired power plants have lower levels of mercury than fish that live farther away.

North Carolina State University researchers say the result may be linked to high levels of another element, selenium, found near coal-fired facilities, which can present problems of its own, a release by the school said.

“We found that fish in lakes located at least 30 kilometers (18 miles) from a coal-fired power plant had mercury levels more than three times higher than fish of the same species in lakes that are within 10 km (6 miles) of a plant,” Dana Sackett, a doctoral student at N.C. State, said. “This information will inform health and wildlife officials who make determinations about fish consumption advisories and wildlife management decisions.”

The results were unexpected since coal-fired power plants are the leading source of mercury air emissions in the world and a significant amount of that mercury is expected to settle out of the air within 6 miles of a plant’s smokestacks.

The researchers theorize lower mercury levels near power plants are likely linked to selenium levels, as fish tested within 6 miles of a plant showed selenium levels three times higher than samples taken from fish located further away. The higher the selenium level, the lower the mercury level, the researchers found.

Selenium, also emitted by coal-fired plants, is known to have an antagonistic relationship to mercury, though the specific mechanisms at work at not completely understood.

High levels of selenium pose their own risks, scientists said.

“Selenium is an important dietary element,” said Dr. Derek Aday, associate professor of biology at N.C. State. “But at high levels, it can have serious consequences — including lethal effects and an array of health problems for fish and wildlife.”

“We actually found the opposite,” Fenton said in a statement. “We found that mice developed deadly, late-stage colon cancer when given high doses of fish oil — more importantly, with the increased inflammation, it only took four weeks for the tumors to develop.”

The study, published in the journal Cancer Research, found an increase in the severity of the cancer and an aggressive progression of the cancer in not only the mice receiving the highest doses of DHA but those receiving lower doses as well.

However, Fenton cautioned people may not need to avoid fish oil — with any nutrient, there is a “bell curve” effect, with those on the left deficient in a nutrient and those on the right in excess.

“Currently, there is a call by academics and the food industry to establish dietary guidelines for omega-3 consumption,” Fenton said. “Most Americans are deficient in omega-3 fatty acids, and there is substantial evidence supporting the beneficial effects of the consumption.”

The findings support a growing body of literature implicating the harmful effects of high doses of fish oil in relation to certain diseases, Fenton added.

LONDON, Oct. 3 (UPI) — A virus that makes frogs bleed to death is wiping them out in much of Britain, biologists said.

The ranavirus has killed off 80 percent of common frogs in the worst-hit areas and threatens other amphibians, a senior research fellow at the Zoological Society of London told The Sunday Telegraph.

Scientist Trent Garner said, “Many of these populations are hanging on by a handful of frogs. If the disease causes the frog populations to fall so low then so many other factors come into play that could cause local extinctions.”

The researchers examined frog numbers in a selection of populations around the country where ranavirus disease has been reported since 1996.

In half of the populations surveyed, there were repeated outbreaks. In almost a quarter of the cases, frog numbers dropped by more than 80 per cent.

Ranavirus is thought to have appeared in Britain in the 1980s, introduced through imported fish or amphibians. The plague was first reported in the southeast England and has spread as far as Manchester, Cornwall and Wales.

DHAKA, Bangladesh, Oct. 1 (UPI) — U.S. researchers said tigers in the Sundarbans forests of Bangladesh weigh about half as much as Bengal tigers in other areas.

The U.S. Fish and Wildlife Service research, carried out by the University of Minnesota and the Bangladesh Forest Department, found the average female Sunderbans tiger weighs 170 pounds, compared to 304 pounds for other wild Bengal tigers in South Asia, the BBC reported Friday.

Adam Barlow, a co-author of the research, said the team is unsure of the cause behind the comparative smallness of the tigers.

“This could be related to the small size of deer available to tigers in the Sundarbans, compared to the larger deer and other prey available to tigers in other parts,” he said.

The team said the Sundarbans tigers could be among the smallest tigers in the world.

Hong Kong’s Center for Food Safety took about 2,700 samples for chemical tests and the remainder for microbiological and other tests, Xinhua news agency reported.

Among the food items failing were frozen suckling pig with excessive levels of a veterinary drug, frozen fish and shrimp with high mercury levels, and some fresh fish with elevated levels of cadmium, Xinhua said.

A sample of Singaporean-style fried noodles was contaminated with bacteria, while other foods were found to contain banned preservative chemicals.

With a display space of half a million square feet, the Tianjin Polar Marine Museum has more than 2,000 polar species from Russia, Canada, Australia and other countries on display, China’s state-run news agency Xinhua reported Thursday.

Visitors at Thursday’s opening could experience a 100-foot-long “touch pond” to touch and feel a selection of fish, shrimps, crabs, shellfishes, marine algae and coral.

Within the museum is a performance venue capable of accommodating an audience of 2,000.

The polar marine museum is part of a “polar marine world” project of Chinese company Haichang (Group) Co. Ltd., which is still under construction.

The investment for the whole project is about $538 million, Xinhua reported.

SYDNEY, Sept. 28 (UPI) — Australian researchers report they’re seeing significant changes in the distribution of coastal fish species they say are partly due to climate change.

Commonwealth Scientific and Industrial Research Organization scientists have identified 43 species, representing about 30 percent of the inshore fish families occurring in Australia’s southeast coastal waters, that exhibited shifts thought to be climate-related, the group said in a release.

These include species such as silver drummer and rock blackfish that are breeding and have become more abundant, and range increases in snapper and rock flathead.

There also is a greater abundance of warm water tuna and billfishes and occasional visits from Queensland groper and tiger sharks, the researchers say.

“Shifts in the distribution of marine animals in response to climate change can be detrimental to some species,” Peter Last, curator of the Australian National Fish Collection, said.

“The problem is that in southern Tasmania, shallow cold water species have nowhere to escape warmer conditions in the sea.”

Last says southeastern Australia is a climate change hot spot with well-documented changes already occurring over the past 70 years, including southward penetration of the East Australian Current by about 200 miles and a temperature rise of almost 3 1/2 degrees Fahrenheit.

SYDNEY, Sept. 28 (UPI) — Australian researchers report they’re seeing significant changes in the distribution of coastal fish species they say are partly due to climate change.

Commonwealth Scientific and Industrial Research Organization scientists have identified 43 species, representing about 30 percent of the inshore fish families occurring in Australia’s southeast coastal waters, that exhibited shifts thought to be climate-related, the group said in a release.

These include species such as silver drummer and rock blackfish that are breeding and have become more abundant, and range increases in snapper and rock flathead.

There also is a greater abundance of warm water tuna and billfishes and occasional visits from Queensland grouper and tiger sharks, the researchers say.

“Shifts in the distribution of marine animals in response to climate change can be detrimental to some species,” Peter Last, curator of the Australian National Fish Collection, said.

“The problem is that in southern Tasmania, shallow cold water species have nowhere to escape warmer conditions in the sea.”

Last says southeastern Australia is a climate change hot spot with well-documented changes already occurring over the past 70 years, including southward penetration of the East Australian Current by about 200 miles and a temperature rise of almost 3 1/2 degrees Fahrenheit.

VIENTIANE, Laos, Sept. 24 (UPI) — Laos says it rejects calls for a dam moratorium on the Mekong River because it wants cheap power to develop its economy despite threats to fish habitats.

The Southeast Asian nation moved this week to secure regional approval for the first major hydropower plant on its stretch of the lower Mekong in the face of protests from international conservation groups, Britain’s Guardian newspaper reported Friday.

The country’s proposed hydropower plant threatens the habitat of the giant Mekong catfish, which can weigh up to 650 pounds, the newspaper said.

Catfish as long as small cars and stingrays that weigh more than tigers are threatened by the proposed 2,600-foot dam, but the government said the economic benefits outweigh the environmental risks.

“We don’t want to be poor anymore,” Viraphone Viravong, director general of the country’s energy and mines department, said. “If we want to grow, we need this dam.”

In a submission to the Mekong River Commission, Laos said it wants to build a hydropower plant at Sayabouly in northern Laos to generate foreign exchange income.

If approved, about 90 percent of the electricity would be sold to neighbors Thailand, Vietnam and Cambodia.

Sayabouly is the first of 11 proposed dams on the lower reaches of the Mekong, a river already heavily dammed upstream in China, the Guardian said.